“They don’t know that we know that they know we know”

Apparently, humans can comfortably keep track of three different mental states at a time.

For example, the proposition “Peter said that Paul believed that Mary liked chocolate” is not too hard to follow. Add a fourth level, though, and it’s suddenly more difficult. And experiments have shown that at the fifth level understanding drops off by 60 percent, Ms. Zunshine said. Modernist authors like Virginia Woolf are especially challenging because she asks readers to keep up with six different mental states, or what the scholars call levels of intentionality.

Perhaps the human facility with three levels is related to the intrigues of sexual mating, Ms. Zunshine suggested. Do I think he is attracted to her or me? Whatever the root cause, Ms. Zunshine argues, people find the interaction of three minds compelling. “If I have some ideological agenda,” she said, “I would try to construct a narrative that involved a triangularization of minds, because that is something we find particularly satisfying.”